Thrust vectoring nozzle

ABSTRACT

A variable geometry exhaust nozzle arrangement includes a plurality of hingable exhaust petals defining a perimeter of an exhaust duct and an annular ring slidably engagable against a radially outer surface of each petal. The annular ring is coupled to a plurality of circumferentially spaced actuator arrangements, each including first and second circumferentially spaced parallel actuator arms pivotably coupled to the annular ring at a first end and to a slide arrangement at a second end. Each slide arrangement is mounted for linear sliding movement relative to the annular ring, such that sliding movement of each slide arrangement causes pivoting of the first and second actuator arms to thereby translate the annular ring in one or both of a longitudinal direction and a lateral direction.

The present disclosure concerns a nozzle such as a gas turbine enginenozzle which can provide thrust vectoring in flight.

In order to increase aircraft maneuverability, it is known to provideaircraft having vectorable exhaust nozzles, so that exhaust from theengine can be directed in a desired direction. Prior designs are knownwhich comprise a plurality of hinged petals, positioned by a series oflinkages. The linkages are in turn mounted to a gimballed ring,controlled by actuators. Such an arrangement is sometimes referred to asan “iris” design, and may permit both thrust vectoring and exhaustnozzle area adjustment. An example prior design is disclosed in U.S.Pat. No. 4,994,660. Vectoring nozzles are also known for directingaircraft exhausts for providing vertical/short takeoff and landing(V/STOL). An example prior V/STOL vectoring nozzle is described in U.S.Pat. No. 3,429,509, which uses a three-bearing swivel nozzle.

Prior “petal” type vectorable exhaust nozzles controlled by a gimballingring allow gaps to form between petals during movement, since thelinkage arrangement is unable to evenly distribute the petals. Somedesigns use an additional link to reduce this effect. However,significant petal gaps still form. On the other hand, three-bearingswivel nozzles can provide for exhaust vectoring, but separate provisionmust be made for exhaust nozzle area modulation, and vectoring can onlygenerally be provided for in one axis.

Similar considerations apply for pump jets, where smaller nozzle areasare desirable to provide for high acceleration and larger areas forefficient cruising, while thrust vectoring is desirable to providesteering. Again, conventional vectorable designs may suffer from similardisadvantages as the above jet engine nozzle designs.

Where gaps form in the nozzle, additional cooling air is required,reducing the performance of the engine. In addition the nozzle hasgreater losses and is less effective.

According to a first aspect there is provided a variable geometryexhaust nozzle arrangement comprising:

-   -   a plurality of hingable exhaust petals defining a perimeter of        an exhaust duct;    -   an annular ring slidably engagable against a radially outer        surface of each petal;    -   the annular ring being coupled to a plurality of        circumferentially spaced actuator assemblies;    -   each actuator arrangement comprising first and second        circumferentially spaced parallel actuator arms pivotably        coupled to the annular ring at a first end and to a slide        arrangement at a second end;    -   each slide arrangement being mounted for linear sliding movement        relative to the annular ring, such that sliding movement of each        slide arrangement causes pivoting of the first and second        actuator arms to thereby translate the annular ring in one or        both of a longitudinal direction and a lateral direction.

Advantageously, the arrangement of the present disclosure provides forboth variable exhaust area and variable exhaust vectoring by translatingthe annular ring in a longitudinal direction and a lateral directionrespectively. Since the ring is mounted for substantially translatingmovement only (and not gimballing movement), gaps are not formed betweenthe petals at any exhaust nozzle position, thereby reducing therequirement for cooling air, and increasing propulsive performance.Furthermore, fewer petals may be required in view of the relativelyconstant gap/overlap between petals at different nozzle positions,thereby reducing weight, complexity, part count and cost.

The exhaust nozzle arrangement may comprise two actuator assembliesspaced approximately 180° from one another. Such an arrangement providesfor both exhaust nozzle area adjustment and thrust vector control in oneaxis. The nozzle may comprise three or more actuator assemblies. Such anarrangement provides for both exhaust nozzle area adjustment and thrustvector control in two axes.

Each slide arrangement may be independently actuable by a respectiveactuator. Each actuator arrangement may comprise one or more of a linearmotor, hydraulic actuator and pneumatic actuator.

The annular ring may be slidably mounted to one of a convergent portionand a divergent portion of the exhaust duct.

The lengths of the first actuator arms may be substantially equal to oneanother.

The exhaust nozzle arrangement may be mounted to one of a gas turbineengine and a pump jet.

According to a second aspect of the disclosure there is provided anaircraft gas turbine engine comprising an exhaust nozzle arrangement inaccordance with the first aspect.

According to a third aspect of the disclosure there is provided a pumpjet comprising an exhaust nozzle arrangement in accordance with thefirst aspect.

The skilled person will appreciate that except where mutually exclusive,a feature described in relation to any one of the above aspects may beapplied mutatis mutandis to any other aspect. Furthermore except wheremutually exclusive any feature described herein may be applied to anyaspect and/or combined with any other feature described herein.

Embodiments will now be described by way of example only, with referenceto the Figures, in which:

FIG. 1 is a sectional side view of a gas turbine engine;

FIG. 2 is a side view of a variable geometry exhaust nozzle of the gasturbine engine of FIG. 1 in a first position;

FIG. 3 is a rear view of the variable geometry exhaust nozzle of FIG. 2;

FIG. 4 is a side view the variable geometry exhaust nozzle of FIG. 2 ina fourth position;

FIG. 5 is a side view of the variable geometry exhaust nozzle of FIG. 2in a second position;

FIG. 6 is a side view of the variable geometry exhaust nozzle of FIG. 2in a third position; and

FIG. 7 is a rear view of the variable geometry exhaust nozzle of FIG. 2in a fifth position.

With reference to FIG. 1, a gas turbine engine is generally indicated at10, having a principal and rotational axis 11. The engine 10 comprises,in axial flow series, an air intake 12, a propulsive fan 13, anintermediate pressure compressor 14, a high-pressure compressor 15,combustion equipment 16, a high-pressure turbine 17, an intermediatepressure turbine 18, a low-pressure turbine 19 and an exhaust nozzlearrangement 20. A nacelle 21 generally surrounds the engine 10 anddefines both the intake 12 and the exhaust nozzle arrangement 20.

The gas turbine engine 10 works in the conventional manner so that airentering the intake 12 is accelerated by the fan 13 to produce two airflows: a first air flow into the intermediate pressure compressor 14 anda second air flow which passes through a bypass duct 23 to providepropulsive thrust. The intermediate pressure compressor 14 compressesthe air flow directed into it before delivering that air to the highpressure compressor 15 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 15 isdirected into the combustion equipment 16 where it is mixed with fueland the mixture combusted. The resultant hot combustion products thenexpand through, and thereby drive the high, intermediate andlow-pressure turbines 17, 18, 19 before being exhausted through thenozzle arrangement 20 to provide additional propulsive thrust. The high17, intermediate 18 and low 19 pressure turbines drive respectively thehigh pressure compressor 15, intermediate pressure compressor 14 and fan13, each by suitable interconnecting shaft.

The nozzle arrangement 20 is shown in more detail in a first position inFIGS. 2 and 3. The arrangement comprises a plurality of petals 23, whichproject in a generally longitudinal direction X to define the perimeterof an annular duct through which gas turbine exhaust flows in use. Eachpetal 22 overlaps slightly with an adjacent petal 22 in order tominimise gaps therebetween, whilst permitting relative movement. Thepetals 22 comprise radially inner “slave” petals 22 a, and radiallyouter “master” petals 22 b. The outer petals 22 b overlap adjacent innerpetals 22 a, with the inner and outer petals 22 a, 22 b being arrangedin an alternating fashion. Only the outer master petals are directlymounted to the ring 24 by the guide rails 30, such that movement of theouter petals 22 b drives movement of the inner petals 22 a, whileallowing sliding movement therebetween.

Each petal is mounted by a hinge 25 at an upstream 26 end, which permitseach petal to pivot about a generally circumferential axis, such that adownstream end 22 of each petal is moveable in a generally radialdirection. Typically, each petal widens in a generally circumferentialdirection from an upstream to a downstream end. Upstream of the hinge 25may be a convergent nozzle section (not shown), which is configured toaccelerate gas turbine engine exhaust to sonic or supersonic speeds. Thepetals are provided at a downstream end of the engine, such that exhaustflows out of the duct defined by the petals to ambient air. Therefore itwill be understood that the positioning of the petals 22 will defineboth the duct final area, and the vector of thrust exiting the nozzle20, and therefore will define the expansion ratio of the nozzle, and thethrust vector.

The nozzle arrangement 20 further comprises an annular ring 24 providedannularly outward of, and surrounding the petals 22. A diameter of thering 24 extends in a direction parallel to a radial plane of the engine,i.e. normal to the longitudinal axis X. The ring 24 in this embodimenthas a larger inner diameter than the outer diameter of the upstream end26 of the duct. It will be understood however that embodiments in whichthe ring 24 has a smaller diameter than the upstream end of the duct areenvisaged.

The annular ring 24 slidably engages against an outer surface of atleast a subset of the petals 22, and in this case to the radially outerpetals 22. In this embodiment, the ring 24 pivotably and slidablyengages with each petal 22 by a guide rail 30, such that the ring 24 canmove in a direction generally parallel to the engine longitudinal axisX, with the petals being urged inwardly by longitudinal movement of thering 24, and outwardly by duct pressure. Other mounting arrangementscould be envisaged, provided that longitudinal translation of the ring24 causes radial movement of the petals 22. Since the inner diameter ofthe ring 24 is greater than the outer diameter of the duct at theupstream end 26, axial translation in a downstream direction causes thepetals to move inwardly, thereby reducing nozzle final area, while axialtranslation in an upstream direction causes the petals to move radiallyoutwardly, thereby increasing nozzle final area.

The annular ring 24 is translatable by a plurality of (three in thisembodiment) actuator arrangements 32 a, 32 b, 32 c. Each actuatorarrangement 32 a-c comprises first and second circumferentially spacedactuator arms 34, 36, which are pivotably mounted at a first, downstreamend to the ring 24, and at a second, upstream end to a slide arrangement38 at an upstream end. Each of the arms 34, 36 is mounted with fixedspacing between the first and second arms 34, 36, that each of the arms34, 36 are parallel to the other of that arrangement 32 a-c, such thatthe arms 34, 36 pivot in unison. Each of the arms 34, 36 of eachactuator arrangement 32 a-c is also of the same length.

The slide arrangement 38 comprises a shuttle 40 slidably mounted to oneor more rails 42. The rails are generally parallel to the enginelongitudinal axis X, such that the shuttle 40 is slidably moveable alongthe axis X. One or more hydraulic actuators 44 are provided for axiallymoving a respective shuttle 40 in the axial direction X (only one ofwhich is shown for clarity). Each hydraulic actuator 44 is controlled bya controller 46, which can provide for independent or collectiveactuation of the actuators 44, as will be described in further detailbelow.

FIG. 5 shows the nozzle arrangement 20 in a second position. Theshuttles 40 of the actuator arrangements 32 a-c have been urged axiallyrearwardly (i.e. in a downstream direction) from their positions shownin FIG. 2. The longitudinal distance each shuttle 40 has been movedbetween the first and second positions is substantially equal, and sothe actuator arrangements 32 a-c can be said to have been movedcollectively or synchronously. As a consequence, each of the pairs ofactuator arms 34, 36 is moved axially, whilst also pivoting relative tothe shuttle and the ring 24, to maintain their parallelism.Consequently, the ring 24 is slid rearwardly along the rails 30 in thedownstream direction, while maintaining the same orientation (i.e. thering 24 does not tilt/pivot/gimbal away from a radial plane). In view ofthe smaller inner diameter of the ring 24 relative to the upstream end26 of the petals 22, and the engagement of the ring 24 against thepetals 22, the downstream end of the petals are urged inwardly, therebyreducing the divergence of the duct, and so the final area of the nozzle20. Since the ring 24 maintains its radial orientation, the petals 22are each urged inwardly to the same extent, such that gaps do not appearbetween the petals in either the first or second position.

Similarly, FIG. 6 shows the nozzle arrangement in a third position, inwhich the shuttles 40 of the actuator arrangements 32 a-c have beenurged axially rearwardly (i.e. in a downstream direction) from theirpositions shown in FIG. 2. In this case, the ring 24 is moved axiallyforwardly, thereby urging the petals 22 outwardly, to increase thedivergence of the nozzle, and so increase the final area.

FIG. 4 shows the nozzle arrangement 20 in a fourth positioncorresponding to a downward vectored thrust nozzle position. In thisposition, the petals 22 are oriented toward the ground when the aircraftis in level flight, to provide either a downward pitching moment, or toincrease lift to assist with takeoff.

In moving the nozzle arrangement 20 from the first position to thefourth position, the controller 46 controls each of the actuatorarrangement 32 a-c independently, i.e. asynchronously. In this case, theactuator arrangement 32 a closest to top dead centre of the engine ismoved rearwardly parallel to the longitudinal direction X. The actuatorarrangement 32 b located at a mid-location is moved rearwardly to alesser extent. The actuator arrangement 32 c is moved forwardlysomewhat, then rearwardly, though to a less extent than the actuatorarrangement 32 a. Consequently, the arms 34, 36 the upstream end of thefirst and second arms 34, 36 of the first actuator arrangement 32 a aremoved axially rearwardly, and are pivoted, whereas the downstream endsare pivoted relative to the ring 24, while staying the same axialposition. Similarly, the arms 32, 34 of the other actuator arrangementsmove in a similar fashion, with their downstream ends pivoting andmoving downwardly, whilst remaining in the same longitudinal position.Consequently, the ring 24 is moved downwardly in a direction normal tothe engine longitudinal axis X, whilst again remaining in the sameorientation, such that the centre of the ring 24 is no longer coaxialwith the centerline of the engine 10.

Since the petals 22 are pivotably mounted to the ring 24 at a pointdownstream of the hinges, the petals 22 are pivoted about theirrespective hinges 26, and so re-oriented in a downward direction by thelateral movement of the ring 24. Consequently, thrust from the nozzle 20is vectored downwardly in the fourth position.

Since the ring 24 moves laterally while maintaining an orientation in aradial plane, the petals 22 are moved evenly. Consequently, gaps betweenthe petals 22 do not open up when the nozzle is moved from the first tothe third position. It will be understood that the nozzle 20 can bemoved to an upward thrust vectoring position in a similar manner, or ina port or starboard orientation using differential movement of theactuator arrangements 32 a-c. Similarly, the actuators 32 a-c can bemoved both collectively and differentially to both adjust the final areaand the nozzle vector simultaneously.

Similarly, FIG. 7 shows the nozzle arrangement 20 in a fifth positioncorresponding to a laterally vectored thrust nozzle position. In thisposition, the petals 22 are oriented toward the port side when theaircraft is in level flight, to provide either a lateral force to assistwith aircraft maneuvers, by providing a yaw moment.

Again, the actuator arrangements 32 a-c are move asynchronously, withthe shuttle 40 of the second actuator arrangement 32 b being movedforward, while the shuttles of the first and third actuator arrangementsare moved rearward. Consequently, the centre of the ring 24 is moved toone side of the engine longitudinal axis, thereby vectoring the thrustto one side, off the engine axis. It will be understood that similarmovement in the opposite direction will provide yawing in the oppositedirection. Similarly, it will be understood that a combination of thesemovements can provide both final area adjustment and nozzle vectoradjustment simultaneously.

It will be understood that the invention is not limited to theembodiments above-described and various modifications and improvementscan be made without departing from the concepts described herein. Exceptwhere mutually exclusive, any of the features may be employed separatelyor in combination with any other features and the disclosure extends toand includes all combinations and sub-combinations of one or morefeatures described herein.

For example, other gas turbine engines to which the present disclosuremay be applied may have alternative configurations. By way of examplesuch engines may have an alternative number of interconnecting shafts(e.g. two) and/or an alternative number of compressors and/or turbines.Further the engine may comprise a gearbox provided in the drive trainfrom a turbine to a compressor and/or fan. Similarly, the fan may beomitted, with all flow passing through the compressors. Such anarrangement is known as a “turbojet”. Alternatively, the engine maycomprise a “low bypass” turbofan, comprising a multi-stage, highpressure ratio fan, which passes a greater portion of flow to thecompressors than in the case of a high bypass ratio, single stage fandesign.

As a further example, the actuators may be hydraulically, electrically,or pneumatically driven.

1. A variable geometry exhaust nozzle arrangement comprising: aplurality of hingable exhaust petals defining a perimeter of an exhaustduct; an annular ring slidably engagable against a radially outersurface of each petal; the annular ring being coupled to a plurality ofcircumferentially spaced actuator assemblies; each actuator arrangementcomprising first and second circumferentially spaced parallel actuatorarms pivotably coupled to the annular ring at a first end and to a slidearrangement at a second end; each slide arrangement being mounted forlinear sliding movement relative to the annular ring, such that slidingmovement of each slide arrangement causes pivoting of the first andsecond actuator arms to thereby translate the annular ring in one orboth of a longitudinal direction and a lateral direction.
 2. Anarrangement according to claim 1 comprising two actuator assembliesspaced approximately 180° from one another.
 3. An arrangement accordingto claim 2 comprising three or more actuator assemblies.
 4. Anarrangement according to claim 1, wherein each slide arrangement isindependently actuable by a respective actuator.
 5. An arrangementaccording to claim 1, wherein each actuator arrangement comprises one ormore of a linear motor, hydraulic actuator and pneumatic actuator.
 6. Anarrangement according to claim 1, wherein the annular ring is slidablymounted to one of a convergent portion and a divergent portion of theexhaust duct.
 7. An arrangement according to claim 1, wherein thelengths of the first actuator arms may be substantially equal to oneanother.
 8. An arrangement according to claim 1, wherein the exhaustnozzle arrangement is mounted to one of a gas turbine engine and a pumpjet.
 9. An aircraft gas turbine engine comprising an exhaust nozzlearrangement in accordance with claim
 1. 10. A pump jet comprising anexhaust nozzle arrangement in accordance with claim 1.